In recent years, the number of recorder devices using recordable optical discs has been rapidly increased, and such recorder devices have come to be adopted not only for domestic applications but also for mobile fields. Further, as one of the conventional recordable optical discs, there is a phase change type disc (hereinafter referred to as “DVD-RAM”) which can record data in both lands and grooves, and also development of mobile devices adopting such phase change type disc recording apparatus has been accelerated.
Hereinafter, a focus control in the conventional DVD-RAM recording device will be described.
A DVD-RAM medium is constituted having lands and grooves, and the optimum focus positions for the land and the groove are different from each other due to such as a step difference between them. So, in the conventional DVD-PAM recording device, the optimum focus positions as the jitter best positions are learned for the land and the groove, respectively, and the focus control is performed with switching the offset values thereof at the boundary between the land and the groove, thereby performing recording and reproduction (refer to Patent Document 1).
Patent Document 1: Japanese Published Patent Application No. 2000-155961 (Page 14, FIG. 9).